Memory is one type of integrated circuitry, and is used in computer systems for storing data. Integrated memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
One type of memory is phase change random access memory (PCRAM). Such memory utilizes phase change material as a programmable material. Example phase change materials that may be utilized in PCRAM are ovonic materials, such as various chalcogenides.
The phase change materials reversibly transform from one phase to another through application of appropriate electrical stimulus. Each phase may be utilized as a memory state, and thus an individual PCRAM cell may have two selectable memory states that correspond to two inducible phases of the phase change material.
A difficulty in utilizing PCRAM is that there can be substantial leakage of current through the memory cells, and such may adversely lead to errors during retrieval of stored data from a memory device. Accordingly, diodes or other select devices are commonly paired with the memory cells to assist in control of current through the memory cells.
Various problems can be encountered in the development of memory array architectures comprising PCRAM cells and select devices. The problems can involve, for example, mask misalignment during the various patterning steps utilized to pattern the memory cells and/or to pattern the select devices.
It would be desirable to develop methods of forming PCRAM cell memory array architectures in which multiple structures of the memory cells and/or associated select devices are fabricated with a common masking step, in that such can reduce masking steps and thereby reduce likelihood of mask misalignment. It would also be desirable to develop improved PCRAM cell architectures.